Patterns of antiemetic therapy and its outcomes in patients undergoing high-dose antineoplastic therapy were studied. The study, conducted at a cancer center, included both a retrospective evaluation of patients undergoing highly emetogenic high-dose chemotherapy with peripheral blood stem-cell rescue between November 1994 and December 1995 and a concurrent evaluation of patients treated between January and May 1996. During the study period the recommended antiemetic regimen for highly emetogenic chemotherapy was a single dose of granisetron 1 mg i.v. daily 30 minutes before treatment on days of chemotherapy. Severity of nausea and vomiting during both the acute phase (from day 1 of chemotherapy to 24 hours after its completion) and delayed phase (from 24 hours to five days after the end of chemotherapy) was graded according to the Common Toxicity Criteria Grading Scale. A total of 59 patients were evaluable; 41 were reviewed retrospectively, and 18 were reviewed concurrently. On day 1 of the acute phase, 53 patients (90%) had no vomiting and 51 patients (86%) had no nausea. The frequency and severity of nausea and vomiting increased on successive acute-phase days, and it was necessary to add other antiemetics. Nausea and vomiting continued to be significant problems throughout the delayed phase; 32 (54%) of the patients had a maximum of grade 3 nausea, and 29 patients (49%) had a maximum of grade 2 vomiting. Substantial numbers of patients who received selective serotonin type 3 receptor antagonists before high-dose antineoplastic agents had significant nausea and vomiting that required the addition of other antiemetics.